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PubMed2003

Eyes absent represents a class of protein tyrosine phosphatases.

The Eyes absent proteins are members of a conserved regulatory network implicated in the development of the eye, muscle, kidney and ear. Mutations in the Eyes absent genes have been associated with several congenital disorders including the multi-organ disease bronchio-oto-renal syndrome, congenital cataracts and late-onset deafness. On the basis of previous analyses it has been shown that Eyes absent is a nuclear transcription factor, acting through interaction with homeodomain-containing Sine oculis (also known as Six) proteins. Here we show that Eyes absent is also a protein tyrosine phosphatase. It does not resemble the classical tyrosine phosphatases that use cysteine as a nucleophile and proceed by means of a thiol-phosphate intermediate. Rather, Eyes absent is the prototype for a class of protein tyrosine phosphatases that use a nucleophilic aspartic acid in a metal-dependent reaction. Furthermore, the phosphatase activity of Eyes absent contributes to its ability to induce eye formation in Drosophila.

Amino Acid Sequence↗
PubMed2002

Distinct regulatory cascades for head and trunk myogenesis.

Most head muscles arise from the pre-otic axial and paraxial head mesoderm. This tissue does not form somites, yet expresses the somitic markers Lbx1, Pax7 and Paraxis in a regionalised fashion. The domain set aside by these markers provides the lateral rectus muscle, the most caudal of the extrinsic eye muscles. In contrast to somitic cells that express Lbx1, lateral rectus precursors are non-migratory. Moreover, the set of markers characteristic for the lateral rectus precursors differs from the marker sets indicative of somitic muscle precursors. This suggests distinct roles for Lbx1/Pax7/Paraxis in the development of head and trunk muscles. When grafted to the trunk, the pre-otic head mesoderm fails to activate Lbx1, Pax7 or PARAXIS: Likewise, somites grafted into the region of the lateral rectus precursors fail to activate the lateral rectus marker set. This suggests that distinct regulatory cascades act in the development of trunk and head muscles, possibly reflecting their distinct function and evolution.

Animals↗
PubMed1992

["Abducens neuromyotonia" with partial oculomotor paralysis].

Paroxysmal involuntary spasms of extraocular eye muscles which can lead to reversible pathological eye positions and limitations of eye movements are etiologically heterogenous. Despite the diagnostic difficulty, they are important as a neurological sign because of the usually good response to treatment. We report on a patient with the unusual combination of ocular neuromyotonia with brief paroxysmal tonic lateral deviation of the left eye and a concomitant partial third nerve palsy. The paroxysmal episodes disappeared with carbamazepine therapy. Possible pathomechanisms are discussed.

Abducens Nerve↗
PubMed1986

[Value of plain x-ray procedures in the diagnosis of ocular muscle paralysis].

Out of 444 patients with paralysis of the eye muscles 187 were examined by plain X-ray films, 144 of were reviewed in order to address the question, whether the X-ray examination was able to elucidate etiology and pathogenesis of the paralysis. Of 444 patients we found positive results in only 14 per cent. Among traumatic, tumorous or inflammatory lesions we found positive results in 47 to 84 per cent of the patients, so that there was reasonable influence on the following diagnostic procedure. Plain films were rarely able to establish a definite diagnosis suitable for therapy. By comparison, computed tomography delivers additional information, so that special procedures could be omitted. In spite of that plain films of the skull should be the first step of the diagnostic algorithm, because they give the right direction to the subsequent expensive procedures.

Humans↗
PubMed1994

Comparative anatomy of cranial nerve motor nuclei: with a comment on evolution of the craniofacial region.

Changes of cranial nerve nuclei are investigated at three crucial points of phylogenesis in frogs, lizards and rats. Profound changes can be observed in the trigeminal and facial motor nuclei parallel to transformation of the primary mandibular joint into the secondary mandibular joint. New muscles appear for mastication and facial expression and they are innervated by new types of neurons. The muscular tongue appears first in tetrapods coinciding with terrestrial life. It can be shown that an entirely new type of neuron develops at the medullospinal junction for the innervation of the intrinsic tongue muscles. These muscles and their neurons are not homologous to somatic muscles and spinal cord neurons. The external eye muscles and their innervation are present from the early craniates through apes in virtually the same pattern of organization. They evolved coincidently with the head and are not homologous to any other structures. It is concluded that if we accept the 'neogenesis' view in head evolution, all contradictions imposed, by the 'segment theory', upon the interpretation and classification of cranial nerve nuclei can be circumvented.

Animals↗
PubMed1971

Alpha and kappa electroencephalogram activity in eyeless subjects.

Several reports have cast doubt on the cerebral origin of alpha and kappa electroencephalogram activity by charging that they are artifacts related to eye activity. Data are cited which eliminate the corneoretinal potential of the eyeball, tremor of the extraocular muscles, eye position, accommodation, and eye flutter as sources of alpha and kappa electroencephalogram activity. A subject with both eyes removed showed normal alpha and kappa electroencephalogram activity. Marked left-right differences in alpha activity were not found in one-eyed subjects whose eyes and extraocular muscles were completely removed on one side.

Adult↗
PubMed1981

Harmaline-induced tremor. II. Unit activity correlation in the interposito-rubral and oculomotor systems of cat.

Units were recorded extracellularly in the cat brainstem under the effect of tremogenic doses of harmaline. They were localized post mortem and the units discharging at the harmaline tremor frequency were mapped. Harmaline-sensitive neurons were found in the bulbo-pontine reticular formation, in particular, in the lateral reticular nucleus and the nucleus reticularis tegmenti pontis. The nucleus interpositus as well as the red nucleus also displayed numerous units discharging at the tremor frequency, indicating that the cerebello-interposito-rubro-spinal system controlling the flexor muscles participate in harmaline tremor. Participation of the oculomotor system in the harmaline-induced tremor was tested at the level of the vestibular neurons relaying the vestibulo-ocular reflex, the motoneurons, the eye muscles and the eye movements. No rhythmic discharge at the tremor frequency nor eye movements could be detected, indicating that harmalie tremor does not affect the oculomotor system.

Alkaloids↗
PubMedDate not supplied

Egocentric visual target position and velocity coding: role of ocular muscle proprioception.

Limited knowledge is available regarding the processes by which the brain codes the velocity of visual targets with respect to the observer. Two models have been previously proposed to describe the visual target localization mechanism. Both assume that the necessary information is derived from the coding of the position of the eye in the orbit, either through a copy of the muscular activation (out flow model) or through eye muscle proprioception (in flow model). Eye velocity coding might be derived from velocity sensitive ocular muscle proprioceptors or from position coding signals through differentiation. We used techniques based on manual pointing and manual tracking of visual target, combined with passive deviation of one covered eye, to demonstrate that ocular muscle proprioception is involved in (i) eye-in-head position coding, hence in target localization function; (ii) long-term maintenance of ocular alignment (phoria); and (iii) sensing of visual target velocity with respect to the head. These observations support other data now available, describing the processes by which the brain codes position and velocity of visual targets. Such findings might interest engineers in the field of robotics who are facing the problem of providing robots with the ability to sense object position and velocity in order to create an internal model of their working environment.

Humans↗
PubMed1990

Ocular muscle proprioception and visual localization of targets in man.

Passive deviation of one eye through 18 degrees, 30 degrees and 42 degrees, achieved by force applied to a sucked-on contact lens, caused the direction of visual targets seen by the other eye to be misjudged in the direction of the passive movement by an amount roughly one-sixth of the angle of passive deviation. The result was the same when the perceived direction was indicated by hand, as when the instant at which a moving target seemed straight ahead was signalled. This result is interpreted by considering that muscular efferents were identical in normal and eye-deviated subjects. The main difference between the two target localization conditions results from the proprioceptor output of the deviated eye. Our data demonstrate that the assessment of the direction of a target seen by an eye that is free to move depends in part on information received by the brain from proprioceptors in the orbit (in our case the contralateral orbit). It would be surprising if the ipsilateral orbit did not contribute as much or more. We therefore consider that this constitutes clear evidence against the pure outflow theory of visual direction judgement (Helmholz, 1867), additional to that provided by the all-or-nothing situation of complete versus incomplete oculomotor paralysis. Two models have previously been proposed to describe the function of the visual localization mechanism. Both assume that the necessary information is derived from the coding of the position of the eye in the orbit, either through a copy of the muscular activation or through eye muscle proprioception. We propose an alternative model in which both afferent and efferent signals from all actively contracted or stretched muscles provide the necessary information to the CNS. The data gathered so far from normal subjects made strabismic with a suction lens, and from a fair proportion of strabismic patients, support our model describing the mechanism of localization of a single punctate target in darkness.

Adult↗
PubMed1989

Effect of botulinum toxin on extraocular muscle proprioception.

Injections of botulinum toxin type A (BoTox) in one extraocular muscle (EOM) induce long lasting paretic lengthening of the muscle permitting realignment to occur in strabismus, while eye movements appear to be unaffected after the transitory period of induced paresis. It has been hypothesized a BoTox-induced change in the spindle discharge of EOMs to explain the effect in EOM length. In decerebrate lambs and goats, first order neurons of eye muscle spindles were identified in a cellular pool located in the medial dorsolateral portion of the semilunar ganglion. The belly of the muscle to which the recorded unit belonged was infiltrated with BoTox. A decrease in afferent discharge of the spindle and in its stretch sensitivity was observed. This effect began 10-15 minutes after the injection. There was no corresponding decrease in muscle tension during the first 45 minutes. This finding suggests that the block of release of acetylcholine at motor endings is earlier and more efficacious in gamma- than in alpha-motoneurons. As a result of the proprioceptive input reduction, an unbalance between the agonist and antagonist muscles should occur favouring the ocular realignment.

Animals↗
PubMed2002

[Dystroglycan linkage and muscular dystrophy].

Dystroglycan is a key complex between basal lamina laminin, extracellularly and membrano-cytoskeleton, intracellularly. The damage of this linkage is turned out to cause muscular dystrophies. Dystroglycan knockout is lethal. Dystroglycan-associated intracellular proteins such as dystrophin, dystrobrevin, sarcoglycans, plectin and caveolin-3 are responsible for causing severe (Duchenne type) and moderate forms (Becker, LGMDs). Laminin, dystroglycan-binding extracellular protein, is deficient in the most severe form of congenital muscular dystrophy with normal intelligence and eye. Recently, a remarkable progress is made in most severe forms of congenital muscular dystrophy with anomalies of brain and eye such as Fukuyama type (Japan) and muscle-eye-brain disease (Finland). The gene product for Fukuyama type, fukutin, belongs to a family of glycosylation enzymes in bacteria and yeast. Since alpha-dystroglycan contains 14-15 o-glycans, ser/thr-mannose 2-1 GlcNAc 4-1 Gal 3-2 Sial in the middle third mucin-domain and the sial-o-glycan is essential for laminin-binding, and since alpha-dystroglycan is defective in Fukuyama type sarcolemma with anti both sugar moiety- and peptide-antidodies, defective fukutin causes incomplete o-glycosylation of alpha-dystroglycan. In '02, it is clarified that a glycosylation enzyme, POMGnT1 which modifies GlcNAc onto ser/thr-mannose, is defective in 6 MEB patients. The loss of the enzyme activity is turned out to lose alpha-dystroglycan from sarcolemma of MEB. These data strongly suggests that o-glycosylation defect of alpha-dystroglycan causes the most severe congenital muscular dystrophy such as Fukuyama type, MEB and Walker Warburg syndrome.

Cytoskeletal Proteins↗
PubMed1980

Observations on Baiji (Lipotes vexillifer) and finless porpoise (Neophocaena asiaeorientalis) in the lower reaches of the Chang Jiang.

Lipotes usually occurs in pairs or in small loose groups. The calves are born in March-April. The Finless porpoises are usually seen in groups of five or six individuals. The blow of Lipotes lasts 0.2-0.6 sec and that of Neophocaena 0.2-0.5 sec. In Lipotes, a short dive would take 10-20 sec and a long dive up to 1-2 min (average value being 31 sec). In Neophocaena a long dive would reach a maximum of 65 sec with an average of 17.5 sec. Lipotes has a pair of functional eyes. The selective secondary atrophy of a number of eye muscles and nerves and the position of the eyes in the head correspond with the physical conditions of the environments, so that the field of vision is directed forwards and upwards. When pursued by motor boat, both species react with a long dive and a change of direction under water. With the Baiji this would occasionally cause fatal injuries by the propeller of the ship. Such a case seems much less often with Neophocaena. The population of Lipotes is at present very small. In the stretch of the river (between Nanjing and Taiyangzhou) under exploration, we found scarcely more than one dolphin per 4 km. The cause for its scarcity is mostly due to accidents or wounds caused by propellers.

Adaptation, Physiological↗
PubMed2006

[Diagnosis of supranuclear eye movement disorders. Part I: different types of eye movements].

The hallmark of a supranuclear eye movement disorder is a functional impairment of one or several types of different eye movements while other types of eye movements still work. All eye movement information is conveyed via the nuclei of the eye muscle nerves. However, the information for a specific type of eye movement is generated in prenuclear cortical and subcortical areas which are activated depending on the type of eye movement performed. Knowledge about the anatomy of these areas enables us to make a clinical diagnosis or to localize the pathological process to a specific area in many neurological conditions. Examination of eye movements are thus a valuable clinical tool in many neurological and neuroophthalmological diseases. The first part of this two-part contribution presents the different types of eye movements, the concept of neural integration, and prenuclear structures important for horizontal eye movement as well as the pertinent pathology. The second part will appear in the next issue and deals with the cerebral structures that are relevant for vertical eye movements including their pathology.

Diagnosis, Differential↗
PubMed1991

Ocular proprioception and efference copy in registering visual direction.

We measured the roles of eye muscle proprioception ("inflow") and efference copy ("outflow") in registering eye position. During monocular fixation, pressing on the side of an occluded eye results in a passive rotation, changing the proprioception without affecting oculomotor efference. As we have shown previously, a constant press on the side of the viewing eye induces active resistance to rotation, changing efference because oculomotor innervation compensates for the eyepress; the viewing eye's fixation remains constant. Using these two types of eyepress, both perceived target deviations and pointing biases in an unstructured visual field were measured in 8 subjects under efference copy, proprioception and control (no eyepress) conditions. Eye deviation was measured photoelectrically. Physiological gains of efference copy and proprioception was about 5/8 and 1/4 respectively. There was no statistically significant difference between perceptual judgement and open-loop pointing. The sum of gains of efference copy and proprioception, about 7/8, indicates incomplete registration of eye eccentricity in an unstructured field, and quantitatively accounts for several previously unexplained results in the literature.

Adult↗
PubMed1977

Computed tomography of orbital lesions. A radiological study of 144 cases.

During the first two years with the 160 x 160 matrix EMI scanner 144 consecutive patients referred with suspicion of orbital disease were subjected to 190 computed tomography (CT) examinations. The X-ray attenuation and enhancement patterns of the various lesions were analyzed. In general it was difficult to correlate these parameters with the histopathological features. Hemangiomas, however, showed little enhancement and meningiomas a large degree of enhancement, while malignancies, lymphomas and pseudotumors were mainly intermediate. With orbital Graves' disease a low preinjection attenuation and a large enhancement (with normal striated neck muscle as a reference) was found in the external eye muscles. The diagnostic accuracy of CT (n=143) was compared to that of A/scan ultrasonography (US, n=80) and carotid angiography (n=40). CT showed the highest accuracy of the three methods, but CT differed only statistically from carotid angiography.

Adolescent↗
PubMed1983

Motility disturbances in Graves' ophthalmopathy.

In a retrospective study of 30 patients with Graves' ophthalmopathy and 25 patients with exophthalmus due to other causes the patterns of ocular motility disturbances and the CT-findings were reviewed. In Graves' ophthalmopathy motility disturbances were found in 83% of the patients, in the control group 26% of the patients showed abnormal ocular motility. Enlarged eye muscles were found in 46% of the patients with Graves' ophthalmopathy and enlargement of the medial rectus muscle was the most consistent finding (42%). A clinical correlation was made between the severity of eye movement restriction and the appearance of the muscle on CT-scan.

Eye Movements↗
PubMed1987

Motoneuronal innervation and mechanical properties of extraocular muscles in the catfish, (Ictalurus punctatus).

Mechanical characteristics and electrical activity were studied in the extraocular muscles of the catfish, Ictalurus punctatus. The contractile properties were determined by stimulation of the individual muscle nerve branches to lateral and medial rectii and the superior and inferior oblique muscles. The speed of contraction was higher than in most other fish muscle, with a twitch contraction time of about 12 ms and a tetanus fusion frequency of 150-170 Hz in all four eye muscles. The fatigue resistance was also high. These properties were the same in fully innervated and partially innervated muscle, largely irrespective of what part of the muscle that was activated. Although different fibre types are known to exist in fish extraocular muscle, it was not possible to obtain functional separation of the mechanical force profile even in the lateral rectus with two distinct motoneuronal innervations. We suggest that polyneuronal innervation of the muscle fibres produces the mechanical responses. Since EMG activity during spontaneous eye movements was similar in the global and the orbital parts of the muscle, all types of fibres in fish extraocular muscle are probably recruited for all types of eye movements.

Animals↗